<!DOCTYPE html>
<html>
<head>
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
  <title>Example Page</title>
</head>
<body>
  <h1>Hello from WebView</h1>
  <button onclick="abc();">扫一扫</button>
  <script>
    function abc(){
        window["app"].postMessage('scan');
    }
    function scan(message){
        alert(message);
    }
  </script>
</body>
</html>
